Metal-oxide-semiconductor (MOS) transistors are the most important devices in modern integrated circuits (ICs). The basic structure of a MOS transistor includes a substrate, a gate structure formed on the semiconductor substrate, and a doped source region and a doped drain region formed in the semiconductor substrate at two sides of the gate structure. The gate structure includes a gate dielectric layer formed on the semiconductor substrate and a gate electrode layer formed on the gate dielectric layer.
With the continuous development of the semiconductor technologies, the control ability of the gate structure of the conventional planar MOS transistor has been reduced; and a severe leakage current issue occurs. Fin field-effect transistors (FinFETs) are a new type of multiple-gate devices. A typical FinFET transistor includes a semiconductor substrate, a plurality of fins protruding from the surface of the semiconductor substrate, a gate structure covering portions of the side and top surfaces of the fins formed on the surface of the semiconductor substrate; and doped source regions and doped drain regions formed in the fins at two sides of the gate structure.
However, when forming semiconductor devices having MOS transistors and/or FinFETs, it is difficult to avoid consuming the isolation layer and to lower process difficulties simultaneously. The disclosed methods and semiconductor structures are directed to solve one or more problems set forth above and other problems in the art.